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99 c1500 suburban issues


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I acquired this vehicle off a trade. And it's been a nightmare to get it running right and I'm hoping someone here might have some insight.

 

The background is this vehicle died while my buddy's wife was driving about a year ago. He figured it was the timing chain. He put a double roller chain on it and got nothing. It was still in pieces when I got it. He still had the old chain. I went and bought the proper chain and put it on. He had chewed up the back of the crank phaser trying to start it but it wasn't bad. I got back together and got nothing. After some trouble shooting I found the crank sensor was shot. Replaced that and got some fire.

 

Since then I've replaced distributor, plugs, wires, coil, and installed the MPFI retrofit kit in it. I've now got it to where it will run but it runs like (insert words a sailor would use when irritated).

 

I've been trouble shooting like crazy. Tried turning the distributor a little to see if i got any difference and got it to a point at which it runs best but still not right. I've double checked the timing chain sprockets, pulled valve covers and double checked valve rockers. Everything is like it should be. Getting 130+ out of each cylinder on compression test. Fuel pressure has yet to drop below 60 lbs. I'm terribly stumped.

 

Just a few minutes ago I decided to go old school. Busted out the timing light to double check timing. Not getting any reading from #1 wire. Timing light might be bad right? Set it on the coil wire and it is working. So I test each plug wire with timing light and 1,6,8 not getting fire through the wires. Now mind you these are brand new wires. Swapped a couple wires getting same result. Start playing with dist cap getting same result. Swap dist cap and getting identical results. Cyl 1,6,8 not being told to fire. Where is the issue? I'm leaning toward bad PCM but not sure. It's so rare that a PCM actually goes bad.

 

I've pulled apart and repaired everything from a chainsaw to an excavator. This is the first Chevy I've ever owned and I'm about to go nuts. Lol. Any thoughts?

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I'm seriously considering scrapping fuel and ignition system and going to a carburetor with an HEI dist. But as much as I've invested getting the vortec system running, I can't be far off.

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That's the cam sensor. And yes I've replaced it.

 

I would think they only used one style vortec motor in the 99. I'm not sure which one it is, but it's the one with spider injection. It's the l31 motor. It's also being a pain in my ass

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There is a small module mounted right next to the coil on a heat sink. I would assume that's the ignition module. But it don't look large enough to control individual cylinder fire.

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Just taking a stab, but did you use a delco cap and rotor? I used an aftermarket brand once and it was defective. I exchanged it under warranty and that one lasted 2 months. I pulled my hair out looking at everything until I found out it was the cap and rotor.

 

Sent from my N9560 using Tapatalk

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I used a timing light to see if spark was going through wires. Knowing absolutely nothing about SBC it's definitely a learning experience. I talked to a buddy of mine and got the motor balancing equation I needed. Pretty sure I've narrowed down. And possibly something that's not a common issue. If you read the original post that's a small book it would be hard to figure out.

 

The crank phaser gear. It was chewed up but still looked operational. Cylinders 1 and 6 are balanced together. Will put in a new crank phazer gear next weekend. If I still have an issue getting spark only thing left is Pcm

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Well I got another phaser ring. Installed it yesterday. Did the trick. Runs like a dream now. If I knew how to post a picture I would put up what was wrong with the old one. Where it slides over the lock key had followed out allowing for it to slide about 8 degrees off from where it's supposed to sit. Now to replace oil pan gasket and do a few other maintenance repairs.

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